In recent years, studies have been conducted on the technology that is called the Internet of things (IoT) and that performs management control by connecting objects, such as home appliances, or the like, to the Internet. As a specific example, there is a known technology in which a sensor included in a device mounted on an automobile or the like measures data, such as temperatures or the like and automatically sends the measured sensor data to a predetermined server device or the like via the Internet.
There is a known service that provides by using this technology by, for example, a service provider the sent sensor data in accordance with a request from a user. For example, if a service user requests sensor data from the server device after specifying the position and the time via a terminal, the server device extracts the target data corresponding to the request from among the pieces of sensor data that are acquired by the devices and provides the extracted data to the terminal. Furthermore, there is also a known technology in which, instead of directly receiving sensor data from each of the devices by a server device, gateways receive the sensor data from each of the devices and provides the received sensor data to the server device.
By the way, examples of the devices connected to the Internet in IoT include mobile terminals, such as smartphones, and movable devices, such as automobiles, or the like. For example, there may sometimes be a case in which, a device is moved after having sent sensor data to a gateway and, consequently, the device sends the sensor data to another gateway located at the move destination. Namely, it is conceivable that the gateway that acquires sensor data measured by a single device differs in accordance with the measurement time. In this case, the server device sends, for example, a request for the sensor data acquired from the subject device to all of the gateways and receives the sensor data from the gateway that has acquired the subject sensor.
In addition, there is also a known technology that holds, in a server device, the move history that indicates that each of the devices sends sensor data to which of gateways at what time point. In this technology, when the server device acquires the sensor data requested by a user, the server device specifies, on the basis of the move history, the gateway that acquires, from the device, the sensor data requested by the user. Then, the server device sends, to the specified gateway, a request for the requested sensor data. Because the server device holds the move history, it is possible to keep a response speed due to a request transmission; however, there is a need to secure the storage capacity for holding the move history.
Patent Document 1: Japanese Laid-open Patent Publication No. 2004-362267
Patent Document 2: Japanese Laid-open Patent Publication No. 2005-123836
Patent Document 3: Japanese National Publication of International Patent Application No. 2014-516504
However, there is the trade-off relationship between keeping a response speed due to holding the move history and reduction in the capacity of the storage device due to deletion of the move history and thus it is difficult to appropriately control the capacity of the move history.
For example, when data is collected from a plurality of gateways, if all of the move histories of each of the devices are held in the server device, an amount of data of the move history is unlimitedly increased as the time has elapsed and there may sometimes be a case in which the capacity of the storage device in the server device is suppressed. In contrast, if the move history is not held or if some data in the move history is deleted, the number of requests sent from the server device to the gateways or the number of requests sent from the requested gateway to the other gateways is increased. Consequently, there may sometimes be a case of a decrease in a response speed with respect to a request for data acquisition.